<my-directive4></my-directive4>
<div class="alert alert-danger" role="alert">
模板字符串需要一个根元素包裹在内
</div>
<pre>
  zppdirective.directive('myDirective4', function(){
    return {
      restrict: 'EA',
      template: '<div>我是一段模板字符串</div>'
    }
  })
</pre>
